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| <h1 class="entry-title">Apache Kudu (incubating) Weekly Update April 11, 2016</h1> |
| <p class="meta">Posted 11 Apr 2016 by Todd Lipcon</p> |
| </header> |
| <div class="entry-content"> |
| <p>Welcome to the fourth edition of the Kudu Weekly Update. This weekly blog post |
| covers ongoing development and news in the Apache Kudu (incubating) project.</p> |
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| <p>If you find this post useful, please let us know by emailing the |
| <a href="mailto:user@kudu.incubator.apache.org">kudu-user mailing list</a> or |
| tweeting at <a href="https://twitter.com/ApacheKudu">@ApacheKudu</a>. Similarly, if you’re |
| aware of some Kudu news we missed, let us know so we can cover it in |
| a future post.</p> |
| |
| <h2 id="project-news">Project news</h2> |
| |
| <ul> |
| <li> |
| <p>The first release candidate for the 0.8.0 release was voted upon last week by |
| the Kudu project members as well as the Apache Incubator PMC. The vote passed |
| on the first try, so this release candidate will is now the official 0.8.0 |
| release.</p> |
| |
| <p>The <a href="http://getkudu.io/releases/0.8.0/docs/release_notes.html">release notes</a> |
| summarize the new features, improvements, and important bug fixes. The |
| release itself and its documentation can be found at the |
| <a href="http://getkudu.io/releases/0.8.0/">Kudu 0.8.0 release</a> page.</p> |
| |
| <p>Thank you to the 11 developers who contributed the 172 bug fixes and |
| improvements for this release!</p> |
| </li> |
| <li> |
| <p>Congratulations to Binglin Chang who was elected as a new committer and |
| Podling Project Management Committee (PPMC) member this past week. |
| Binglin has contributed many bug reports and fixes and new features, |
| and has also given several presentations about Kudu. He is also the |
| first community member to run a Kudu cluster in a real production workload. |
| Thanks for your contributions, Binglin!</p> |
| </li> |
| </ul> |
| |
| <h2 id="development-discussions-and-code-in-progress">Development discussions and code in progress</h2> |
| |
| <ul> |
| <li> |
| <p>Darren Hoo reported an issue on the mailing list where his Kudu daemons were |
| occasionally crashing in a workload involving large string cell values on the |
| order of tens of KB. Todd Lipcon investigated the issue and provided a <a href="http://gerrit.cloudera.org:8080/2725">bug |
| fix</a>.</p> |
| |
| <p>It turns out that this bug has been present since the third week of Kudu |
| development in 2012. Given that the bug persisted so long, yet it was |
| relatively easy to reproduce, it highlights that Kudu needs further |
| testing for use cases with larger cell values. In particular, large |
| primary keys or updates containing large cells would trigger this problem.</p> |
| </li> |
| <li> |
| <p>Activity picked back up on the <a href="http://gerrit.cloudera.org:8080/#/c/2642/">design document for the Replay Cache feature</a>. |
| This feature’s goal is to allow more transparent failovers between Kudu |
| servers and allow operations to be retried without affecting the semantics |
| seen by clients.</p> |
| |
| <p>As an example, consider the case when an ‘INSERT’ operation of a single |
| row times out. Upon receiving a timeout response, the client does not know |
| whether the time out occurred before the insert was processed, or after. |
| The client may then retry the operation, perhaps on a different replica. |
| If the original operation was in fact successfully applied before the |
| timeout occurred, the client might receive an erroneous “row already exists” |
| error.</p> |
| |
| <p>The “replay cache” feature, currently being designed by David Alves, is |
| meant to avoid this issue: each server will keep a relatively small cache |
| of recently applied operations so that, if a retry arrives, it can |
| correctly respond with the original result rather than applying it a second |
| time.</p> |
| </li> |
| <li> |
| <p>Binglin Chang reported an interesting bug where <a href="https://issues.apache.org/jira/browse/KUDU-1391">two of three replicas were |
| online, but neither one was being elected as leader</a>. |
| The issue occurred on his 70-node cluster after accidentally shutting down |
| about half of the servers for ten minutes. Upon recovery, one out of the |
| thousands of tablets got stuck in this situation. Mike Percy and Todd Lipcon |
| have been discussing the issue on the JIRA and seem to be converging on |
| some action items to prevent it from reoccurring.</p> |
| </li> |
| <li> |
| <p>Benjamin Kim revived an old thread about running <a href="http://markmail.org/thread/mznrulrh3o4625ei">Spark on Kudu</a>. |
| Users on the thread are piping up to write about their Spark use cases. |
| It seems likely that, given this interest, some Spark-on-Kudu improvements |
| will be happening in the near term. If you are interested in contributing, |
| please pipe up on the mailing list.</p> |
| </li> |
| </ul> |
| |
| </div> |
| </article> |
| |
| |
| </div> |
| <div class="col-lg-3 recent-posts"> |
| <h3>Recent posts</h3> |
| <ul> |
| |
| <li> <a href="/2016/06/21/weekly-update.html">Apache Kudu (incubating) Weekly Update June 21, 2016</a> </li> |
| |
| <li> <a href="/2016/06/17/raft-consensus-single-node.html">Using Raft Consensus on a Single Node</a> </li> |
| |
| <li> <a href="/2016/06/13/weekly-update.html">Apache Kudu (incubating) Weekly Update June 13, 2016</a> </li> |
| |
| <li> <a href="/2016/06/10/apache-kudu-0-9-0-released.html">Apache Kudu (incubating) 0.9.0 released</a> </li> |
| |
| <li> <a href="/2016/06/06/weekly-update.html">Apache Kudu (incubating) Weekly Update June 6, 2016</a> </li> |
| |
| <li> <a href="/2016/06/02/no-default-partitioning.html">Default Partitioning Changes Coming in Kudu 0.9</a> </li> |
| |
| <li> <a href="/2016/06/01/weekly-update.html">Apache Kudu (incubating) Weekly Update June 1, 2016</a> </li> |
| |
| <li> <a href="/2016/05/23/weekly-update.html">Apache Kudu (incubating) Weekly Update May 23, 2016</a> </li> |
| |
| <li> <a href="/2016/05/16/weekly-update.html">Apache Kudu (incubating) Weekly Update May 16, 2016</a> </li> |
| |
| <li> <a href="/2016/05/09/weekly-update.html">Apache Kudu (incubating) Weekly Update May 9, 2016</a> </li> |
| |
| <li> <a href="/2016/05/03/weekly-update.html">Apache Kudu (incubating) Weekly Update May 3, 2016</a> </li> |
| |
| <li> <a href="/2016/04/26/ycsb.html">Benchmarking and Improving Kudu Insert Performance with YCSB</a> </li> |
| |
| <li> <a href="/2016/04/25/weekly-update.html">Apache Kudu (incubating) Weekly Update April 25, 2016</a> </li> |
| |
| <li> <a href="/2016/04/19/kudu-0-8-0-predicate-improvements.html">Predicate Improvements in Kudu 0.8</a> </li> |
| |
| <li> <a href="/2016/04/18/weekly-update.html">Apache Kudu (incubating) Weekly Update April 18, 2016</a> </li> |
| |
| </ul> |
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